Certain wireless communication functions may require accurate measurement of the signal transit time between two devices. For example, accurate measurement of the signal transit time between two devices can yield an accurate estimate of the physical distance between the two devices as related to the transit time by the speed of light).
Under the IEEE Std 802.11v-2012, the time resolution for such measurements is 10 ns, which corresponds to a distance of about 3 m. Proposals exist to update the 802.11v standard to accommodate higher bandwidths include a time resolution of 0.1 ns, which corresponds to a distance of about 3 cm, which is much more useful for location services. However, uncertainty in the time needed for a signal to propagate from the transmitter output to the antenna through analog RF circuitry (commonly referred to as “transmit delay”), or from the antenna to the receiver input through the analog RF circuitry (commonly referred to as “receive delay”), may be on the order of the proposed resolution, and therefore makes precise measurements of time, and therefore distance, difficult.